Quaternary ammonium salts (QASs) have been known and widely used for more than half a century as disinfectants. It is now accepted that they exert their biocidal activity by an electrostatic mechanism with the cell wall of bacteria. Surfaces coated with QAS-containing polymers retained their activity over a longer period of time. Polysiloxanes with QAS groups are attractive as biocidal polymers as polysiloxanes have high chain flexibility which allows easier contact between microorganisms and QAS. QASs with long alkyl chains are good candidates for this function, as structure, density, and distribution of QASs in the polymer matrix may affect their biocidal activity. A typical coating formulation containing QAS has large number of variables including: the types of QASs; levels of QAS addition; molecular weight of polysiloxanes; levels of catalyst; and the amount of crosslinker.
Silver is another widely-used antimicrobial agent, and it is known that silver species exert their biocidal activity through a leaching mechanism. Previous work has shown that the addition of silver nanoparticles or silver salts to silicone coating solutions generally results in poor dispersion of the silver nanoparticles or silver salts in the silicone coating. This may be due to the nonpolar nature of silicones.